1. Technical Field
The present invention relates to a vehicle headlamp configured to form a light distribution pattern having a cut-off line formed at an upper end portion thereof, by means of a lamp unit of the so-called projector type.
2. Related Art
A related art vehicle headlamp is configured to emit light ahead of a vehicle by means of a lamp unit of the projector type.
The related art projector type lamp unit is configured such that light originating from a light source disposed in the vicinity of an optical axis extending in a longitudinal direction of a vehicle is gathered and reflected toward the front and around the optical axis by a reflector. The thus-reflected light is emitted ahead of the lamp by a projection lens provided in front of the reflector.
When a light distribution pattern having a cut-off line formed at an upper portion thereof is formed by means of the lamp unit, a shade is disposed in the vicinity of a rear focal point of the projection lens. A portion of the light reflected from the reflector is interrupted by the shade, to thus form the cut-off line.
Japanese publication JP-B-6-48601 describes a shade configured to enable selection between a light distribution pattern for a left-distributed low beam and a light distribution pattern for a high beam, serving as a light distribution pattern resulting from emission of light from the lamp unit. The light distribution is done by pivoting the shade—which is configured to pivot about a horizontal axis extending in a transverse direction of a vehicle—in accordance with a vehicle driving condition. JP '601 further suggests, as a modification, the ability to select a light distribution pattern for a right-distributed low beam.
European Patent Application Laid-Open No. 1033528 describes a shade configured such that two areas in an outer peripheral surface of the shade formed from a rotary shaft member, the shaft member configured to pivot about a horizontal axis extending in a transverse direction of a vehicle, are configured as a region to be used for generating a light distribution pattern for a left-distributed low beam (hereinafter simply called a “left low beam light distribution pattern”) and another region to be used for generating a light distribution pattern for a right-distributed low beam (hereinafter simply called a “right low beam light distribution pattern”).
However, the related art has various problems and disadvantages. For example, but not by way of limitation, the shade described in JP '601 is configured such that a plurality of blades is fastened to a rotary shaft member at predetermined intervals in a circumferential direction thereof. To generate a light distribution pattern having a cut-off line formed at an upper end portion thereof by means of the shade, the blade must be configured to accurately stop at a predetermined rotational angular position. To this end, accurate control of rotational movement of the shade is required.
In contrast, the shade described in European '528 generates the left low beam light distribution pattern or the right low beam light distribution pattern via the outer peripheral surface of the rotary shaft member. Hence, if some degree of displacement has arisen in the rotational angle, no essential change arises in the shape of the cut-off line. Hence, a necessity for accurate control of rotational movement of the shade is obviated.
However, the shade described in European '528 encounters a problem of a failure to form a light distribution pattern for a high beam.